Telephone-exchange system.



N0. 646,695. Patnted Apr. 3, I900. w. n. GHARKY & E. E. CLEMENT.TELEPHONEEXCHANGE SYSTEM.

(Application filed 1m 20, 1898.)

(No Model.)

ms' NORRIS Farms 60.. morauwa. WASHING'KON: n. c.

No. 646,695. Patented Apr. 3, I900. W. D. GHARKY &;'E. E. CLEMENT.

TELEPHONE EXCHANGE SYSTEM.

(Application filed Aug. 20, 1898.) .(No Model.) 2 Sheets-Sheet 2.

S SB

WITNESSES THE Noam: PETERS cu, vflo'roumou WASHINGTON. a c.

UNITED STATES.

PATENT @EEICE.

WILLIAM D.. CHARKY, or PHILADELPHIA, PENNSYLVANIA, AND EDWARD E.CLEMENT, OF WASHINGTON, DIsTRICT OF COLUMBIA, AssICNORs TO THE sUNELECTRIC MANUFACTURING COMPANY, OF NEW JERSEY.

"TELEPHONE-EXCHANGE SYSTEM.

sPEoIEIcATIoNarming part of Letters Patent No. 646,695, dated April 3,1900. Application filed August 20, 1898. Serial No. 689,120. (No model.)

To all whom it may concern:

Be it known that we, WILLIAM D. GHARKY, residing in the city and countyof Philadelphia, State of Pennsylvania, and EDWARD E.

CLEMENT, residin gin the city of Washington, District of Columbia,citizens of the United States, have invented certain new and usefulImprovements in Telephone-Exchange Systems, of which the following is aspecification.

to Our invention relates to systems for tel'ephonic interconnectionwherein a central Ofiice or offices is or are provided, subscriberslines radiating therefrom to substations, 1 Where they are provided withtelephonic and I5 signaling apparatus.

The invention relates particularly to such systems of this character asare known as divided central or trunking systems, and it constitutes animprovement upon the particular system described and claimed in ourjoint application for patent, Serial No. 689,119, filed August 20, 1898..According to the in Vention set forth in said application conversationis carried on overmetallic or series circuit, while signaling issimultaneously permitted to be carried on over multipled 0r phantomcircuits. The various steps in connecting and disconnecting subscribersare performed by two (2) sets of operators called, respectively, forconvenience, A and B operators. Each A operator is provided withterminal plugs and communicating cords therefor which she uses in theordinary way for interconnecting subscribers upon her own section. EachBoperator, on the other hand,

devotes her entire time and attention to fin-,

ishing connections which ha've'been trunked by the answering A operatorsat their sectionsthat is to say, the B operators attend 0 to thecompletion of trunk-calls and to those only, while the A operatorsattend to all other business. In order to permit the A operators to keeptrack of the condition of the lines, certain supervisory signaling meansare pro- 5 vided. In the application aforesaid said means consist in apolarized relay. In order to apprise the B operators of connectionsinitiated on the trunk-lines of the A operators, trunk-signals have beenused. These trunksignals receive the current from the main sourcethrough the calling-jack and the answering-plug circuit. In order toprevent this current from operating the supervisory signal beforereferred to, the expedient of polarization was adopted. The principalchange 5 5 in the construction thus described,which constitutes theimprovement to be covered in the present application, is the abolitionof individual trunk-signals and the consequent permissible reduction ofthe polarized supervi- 6o sory relay to a simple ordinary low-woundrelay. In place of the individual trunk-signals we use in the presentsystem individual operators signals, each of which is common to a numberof trunk-terminals. These are arranged to be operated whenever theoperators conversation-circuits are crossed without any especial act orthought on the part of either operator.

Our invention is fully illustrated in the ac- 7o companying drawings,wherein like letters and figures of reference refer to the same partsthroughout.

In said drawings, Figure l is a diagrammatic View of the circuitconnections of two subscribers whose line-terminals are located upondifierent switchboard-sections. Fig. 2 is a detailed view of the circuitat each subscribers station. Fig. 3 is a diagram of the circuits of anumber of operators, showing their signals. Fig. 4 is a diagramillustrating the use of a Wheatstone bridge in the signal ing-circuits.

Referring to Fig. 1, X and Y are two suloscribers stations, eachprovided with a complete telephone set comprising the usual transmitterand receiver. From the middle point of the windings of the receiver Awire 9 is led to the ground and the receiver-windings are interposedbetween the divided o halves of the secondary winding of the subscribersinduction-coil.

The instruments, as shown in Fig. 1,-are

'supposed to be in position for use and the details of their-circuitsare not shown; but upon reference to Fig. 2 it will be seen that theline-wires 1 and 2 during the non-use of the instrument and while thereceiver is hanging upon the switch-hook are bridged by the circuit ofthe bell or ringer Q and disconmo j when the plug is in the jack.

nected from the conversation-circuit. \Vhen' the receiver is removedfrom the hook, however, the levers H and it rise under the influence ofa suitable spring and after breaking the bell-circuit make a circuitover the linewires 1 and 2 through the local connections 18 and 19, thesecondary U of the inductioncoil and the receiver, the middle point ofwhose windings is connected to ground through the wire g, and at thesame time the local translnitter-circuit 20, including the transmitterand the primary u of the induction-coil, to gether with a suitablebattery, is closed.

The line-wires 1 2 and 3 t terminate in jackspringsjj upon thecentral-olfice switchboardsections. Each pair of line-wires is bridgedprior to its connection with the jack-springs by an impedance-coil I,from the middle point of which a wire 5 is led to one winding Z of theline-annunciator L, and thence by the wire 6 to the main battery M andto ground. The annunciator I, is provided with a differential winding Z,one end of which is connected to the wire 6 and the other to thespringj, which is adapted to be connected by a collar upon theconnecting-plug with a twin springj, from which a wire leads throughresistance Rh to ground. All of the apparatus thus described issubstantially the same as that in our prior application above referredto.

Each A operator is provided with pairs of plugs P P, plug P having a tipand sleeve 1) and p, which are connected, respectively, to the sleeveand tip of plug P, although this order of connection is not essential,being revel sible, if desired. The plug P also has a collar 13 which isinsulated from the tip and sleeve and whose function is to connect thesprings The plugs P and P are connected by the cord conductors 7 S. Arelay Nis provided for each pair of plugs, its windings being connectedin parallel in the two sides 7 and 8 of the plug-cord circuit. By thisarrangement the relay will only be energized by currents passingtherethrough in multiple. The armature n of this relay is adapted whenattracted to close a local circuit 18, containing a suitable battery .9and a signal, shown as an incandescent lamp n.) Anordinary ringing-keyis also provided for each cord-circuit, which upon its actuationconnects the circuit of a generator with the plug P. The said plug Prests in a seat which is provided with contact-springs pp, adapted totouch the sleeve and tip contacts of the plug or external rings thereon,respectively, connected thereto, and to thereby continue the two sidesof the plugcord circuit 7 8 to the A opcrators listeningcircuit 11 12.

The plugs P P, with their associated apparatus, sutlice for theconnection of subscribers whose line-terminals are near together; butwhere, as shown in Fig. 1, connection is necessary between subscribersupon dilferent switchboard-sections trunk-lines 9 10 are used, eachtrunk-line terminating at one end in a jack J and at the other end in aplug P All the jacks J of a given group of trunklines which interconnectany one board with another are grouped together before the A operator atthe first board, while their plugs P are grouped together before the Boperator at the other board. The listening-circuit 11 12 of the Aoperator terminating in'her telephone set 0 is branched to all thesetrunklines and also to all the other switchboardsections. Conversely,the listening-circuit 13 14 of each B operator terminating in hertelephone O'is branched to the jacks J 2 of all the trunk-lines leadingto her board. \Vithin each trunk-jack J a circuit-closer C is providedhaving a plunger 0, adapted to be depressed under certain conditions bya plug inserted in the jack, to thereby spread apart springs c 0 formingthe terminals of the B operators circuit 13 14 and cause them to makecontact with anvils c c, constituting terminals of the A operatorscircuit 11 12. Before each B operator and in proximity to hertrunk-terminals a similar switch 0 is provided, having a plunger 0,which upon depression spreads apart springs c and 0 which form terminalsof the A operators circuit 11 12, causing them to make contact withanvils 0 0 connected with the two sides 13 14 of the B operatorscircuit. In proximity to the trunk-plugs P and connected to the Boperators circuit is also provided a jack J.

In order that signaling may be carried on between the operators, thefollowing means are provided: A wire 17 is led from the middle point ofthe windings of the A operators telephone 0 through the battery S and toall the other switchboard-sections. From the middle point of thewindings of each B operators telephone 0 a wire 10 is led out. Beforeeach B operator an annunciator is located provided with a shutter a andhaving its winding 10 connected on one side to wire 16 and on the otherto wire 17. Only one of these annuneiators is shown herein; but it willbe understood that the wire 16 of each B operator serves as a commonconnection for all the wires 17 of the A operators at different boards,and, conversely, each wire 17 of an A operator is cross connectedthrough various annunciator-windings to with the respective wires 16.

The operation of our system thus described is as follows: Subscriber Xdesiring to converse with subscriber Y removes his telephone-receiver Rfrom the hook II, whereupon the latter and its connected lever riseunder the influence of the spring and complete the talking-circuit shownin Fig. 2.

Current will then flow from the battery M through the wire 6, thewinding Z, wire 5, the two halves of the coil I and the line-wires 1 2in parallel to the subscribers station and there through the wires 1819, the two halves of the secondary U and the two halves ofthereceiver-winding, the wire g, and ground back to the battery. Theannunciator L thereupon displays its signal and the A operator at thatboard perceiving the signal inserts the plug P in thejackJcorrespondingthereto. Inasmuch as the plug P remains in its seat a talking-circuit isimmediately completed without any further act on the part of theoperator from the subscribers instrument to her set 0. Havingascertained the connection desired and finding it to be with thesubscriber Y, who is located on another board, the A operator removesthe plug P from its seat and inserts it in the jack J of the trunk-lineleading to the desired board. In so doing the A operator presses theplug P into the jack farther than is required simply to make connectionwith the jack-springs, the tip of the plug thereby depressing theplunger and spreading the springs c and into contact with the anvils cand 0 A complete metallic circuit is thus established between the A andB' operators sets 0 and O. Incidentally the signaling-circuit throughthe annunciator A before the B operator and corresponding to the Aoperator is completed as follows: from the battery S through wire 17,through the split windings of the telephone 0, through the wires 11 12in parallel, anvils c 0 springs c 0 wires 13 14 in parallel, splitwindings of telephone 0, wire 16, winding w, wire 15, and back to thebattery. The A operator is thus enabled to instruct the B operatordirectly as to the number of the subscriber wanted, and while in suchinstructions she gives the number of the trunk-line and of thesubscriber wanted the annunciator A performs the function of directingthe B operators attention immediately to the proper group oftrunk-plugs, and in case the B operator should happen to be temporarilyengaged furnishes a continued indication that she has been called by theA operator, to whose board said trunk-lines are extended. Upon receivingher instructions the B operator inserts the plug 1) in the jack J of thesubscriber Y. Current will then immediately flow from battery N throughWire 6, winding Z, wire 5, impedance-coil I, and jack J of the calledsubscriber, through plug P trunk-wires 9 10, jack J plug P, cordconnection 7 8, the two halves of the Winding of relay-magnet N, plug P,jack J, line wires 1 ,2, and to ground through the wire 9 of the callingsubscriber. This current energizes the magnet N, which thereuponattracts its armature n, closing circuit 1S and displaying the signalit. This apprises the A operator of the insertion of the plug p andimmediately upon perceiving the signal n she depresses the calling-keyK, which connects the generator through the plug P and the trunk-line tothe called subscribers line to ring his bell. The signal a re-' mallydisconnected.

flowed back through the connecting-circuit to the calling-subscribersstation, is diverted through the line-wires3 4 to ground at the stationY. Currentnolongerpassingthrough the connecting-circuit, the magnet Nreleases its armature and the signal n is retired, thus apprising the Aoperator of the fact that the subscriber Y has'answered the call. 7

Referring to Fig. 3, which is a diagram of the instruction-circuits ofthree A girls and three B girls with their signals, the A girlspositions are shown at O, 0 and 0 the symbols which are so letteredbeing supposed to represent, diagraphically, operators headphones withthe caps removed to show the coils 0 and 0. From eachAgirls position toeach B girls position (the latter shown at 0, O and 0 extends aninstruction-circuit. That from girl 0 is numbered 11 12, and, as clearlyshown, it passes to the B girls positions, crossing all their circuits,which are numbered 13 14, 13 14, and 13 14. The circuit from theposition 0 is lettered 11 12 and that from position 0 is 11 12 each ofthese likewise crossing all the B girls circuits at the left of thefigure, but all being nor- Conversely to the above the circuits 13 14,13 14 and 13 14 pass from the head-phones O, 0 and O to the A girlspositions, where each of them is carried across or past all the A girlscircuits. At the place of intersection of the circuits 11 12 and-13 14at the right-hand side of the figure we have shown a pair of bent lines,which are intended to represent a switch which may be turned to connectwire 11 with wire 13 and wire 12 with wire 14. In reality theseswitches, which are lettered C, are made as shown in Fig. 1, where aplunger 0 acts upon springs c and c to cross the operators circuits.These switches are all located at the trunk-jacks on the A sections, butthe trunklines are omitted from Fig. 3 and the switches reduced to theirsimplest elements in order to prevent confusion. Obviously when anyswitch 0 is actuated the operator 0, 0 &c., has crossed her circuit withthat of the corresponding B operator, according to which switch is used.From a point midway of the windings of the telephone 0 the Wire 17 isled out and passes to theB operators positions, where it forms a commonreturn for the annunciator-coils to, 10, and 10 located, respectively,opposite the B girls, whose headphones are indicated at O, 0 and OSimilarly a wire 17 passes from the middle point of the windings ofoperators telephone 0 and forms a common return for the three coils w,10 and 10 while the wire 17 passes from a telephone 0 to form a commonreturn for-the windings 10 10 and 20 Thus there is an annunciator-coilopposite eachB girl for each A girl. From the middle point of thewindings of telephone 0 the wire 16 is led out to form a common returnfor the three coils w, w, and 20 From the telephone 0 a similar wire 16?is connected to three coils 10, to and @0 while from telephone 0 thewire 16 forms a common return for the coils 10 10 and 10 Now suppose theoperator at O is using a trunk-line to actuate the left-hand switch 0 ather position- She thereby connects the wires 11 12 with the wires 13 14,and not only are the telephones 0 and 0 connected on the metalliccircuit, but the following circuit is completed: from battery S by wire17 to telephone O, and thence by wires 11 12 in parallel to switch 0,thence by wires 13 14 in parallel to telephone 0 by wire 16 to theannunciator w, and by wire 17 back to the battery. The annunciatorthereupon displays its signal, telling the first B girl that the first Agirl is calling her. By manipulating the other two switches O oppositethe telephone 0 the first A girl can send current from the batteries Sand S at will through the annunciators 10 and 20 Similarly the girl 0can work any one of the annunciators w, 10 and 20 according to whichoperators circuit she connects herself with.

The switches 0 enable the B operators to connect their circuits withthose of the A operators for further instructions, &c.

Fig. 4 shows in the simplest possible way the distribution of currentupon which de pends the operation mentioned. In this figure X and Y arethe subscribers stations, having switches H each adapted to ground theline. The cord-circuit, includinga trunkline when a connection has beencompleted, is shown extending from J to J, and the supervisory signal isindicated by a galvanometer N. Supposing X to have called, current isflowing from battery M through the left-hand line 1 2 and to ground atstation X, and thence back to battery. The operators have made theconnection from J to J and the subscriber Y has not yet answered-i. 6.,he has not yet worked his switch to ground the line. Current frombattery M will now find two paths, one from the battery direct tostation X and ground via the point J, and the other by way of point Jacross through the galvanometer N to point J, and then out to station Xand ground. The internal resistance of the battery being small, enoughcurrent flows through the branch containing the signal to operate thesame. hen subscriber Y answers the call by grounding his line, it mustbe obvious that a true Wheatstone bridge is produced. The galvanometer Nis in the bridge-wire, and as long as the resistances of lines 1 2 and 31 are approximately the same there will be no current in the bridge whenboth lines are complete. If either subscriber should hang up histelephone, and thereby remove the ground from his line, we evidentlyhave a break (or an infinite resistance) in one side of the bridge, andwhichever side it is the bridge-wire with galvanometer N will receivecurrent. In applying this to the diagram Fig. 1 it must be borne in mindthat for signaling purposes the component wires of the metallic circuit1 2 and 3 4: are one. The cord and trunk circuits are also singleconductors, so that for signaling purposes the conditions are exactly asshown in Fig. 4. One advantage of this bridge construction is thatwhenever both subscribers have finished a conversation and hung up theirreceivers the magnet N will not respond, but both line-signals will showfor clearing out.

Having thus described our invention, what we claim, and desire to secureby Letters Patent, is-

1. In a telephone-exchange system, operators metallicinstruction-circuits for conversation normally disconnected, a separatecircuit containing battery and a signal extending between the operators,said circuit composed in part of the different instruction-circuits,whereby when an operator connects her instruction-circuit with anotheracorrespond ing signal is thereby given to the other operator,substantially as described.

2. In a telephone-exchange system a series of metallicinstruction-circuits adapted to be crossed at will to permitcommunication between operators, a series of signaling-circuitscross-connecting the operators in such a manner that eachinstruction-circuit forms a common return for all the signaling-circuitsleading to any operator, together with suitable signals and batteries insaid circuits, substantially as described.

3. In a telephone-exchange system operators metallicinstruction-circuits adapted to be crossed together at will, and eachcontaining one operators telephone, signaling-circuits, each containingbattery and connected to an operators telephone at one end and branchedto a number of other operators telephones, together with a signal ineach branch, whereby the crossing of one operators instruction-circuitwith another will operate the signal indicatory of the first operator infront of the other operator, substantially as described.

4. In a telephone-exchange system, operators divided into two sets,conversation-circuits between each operator of one set and all theoperators of the other set, a signalingcircuit associated with andcompleted through the circuit of each operator of the first set, andbranched through annunciators distributed before the operators of thesecond set to their circuits, whereby when the circuit of an operator ofthe first set is crossed with that of one of the other set, theappropriate signal before the second operator is automaticallydisplayed, substantially as described.

In testimony whereof we have hereunto set our hands, this 15th day ofAugust, A. D. 1808, in the presence of two witnesses.

WM. D. GHARKY. EDWARD E. CLEMENT.

\Vitnesses:

ROBERT OSBORNE, J12, EMERSON CONRAD.

ICC

